Method For Reducing Differentiation Resistance Of Pluripotent Stem Cells

ABSTRACT

In related-art methods of differentiating pluripotent stem cells into a desired cell type, there has not been established a differentiation induction method using human ES/iPS cells and being stable and highly efficient. A method of inducing differentiation into a desired cell type within a short period of time and with high efficiency by attenuating differentiation resistance of a pluripotent stem cell to generate a pluripotent stem cell that actively proceeds to a differentiated cell type has been found, and thus the present invention has been completed.

TECHNICAL FIELD

The present disclosure relates to a method of attenuating differentiation resistance of a pluripotent stem cell to a desired cell type, and more specifically, to a method of differentiating a pluripotent stem cell into a desired cell type with high efficiency and a differentiation inducer to be used for the differentiation method.

The present application claims priority from Japanese Patent Application No. 2015-211356, which is incorporated herein by reference.

BACKGROUND ART

(On Induction of Differentiation of Pluripotent Stem Cells)

Regenerative medicine using cells obtained by inducing differentiation of embryonic stem cells (ES cells) or induced pluripotent stem cells (iPS cells) is a therapeutic method for which the people have high expectations and which is desired to be realized soon. As regenerative medicine, a transplantation therapy with retinal pigment epithelial cells derived from iPS cells is fresh in memory. However, a technology for generating mature differentiated cells suited for cell transplantation rapidly and in a sufficient amount is still under development and has huge room for development.

A currently mainstream method of inducing differentiation of pluripotent stem cells into a desired cell type is a method involving sequentially adding cytokines/growth factors suited for respective differentiation stages to a medium to cause differentiation via an embryoid body and progenitor cells. This method has problems in, for example, that a culture period until differentiated cells of interest are obtained is long, that differentiation induction efficiency is not high, and that cells of different cell lineages are mixed with each other.

In recent years, attempts have been actively made to direct cell differentiation by forcibly expressing, in ES/iPS cells, one or a combination of a plurality of tissue-specifically expressed transcription factors. This differentiation induction method using transcription factors can directly induce ES/iPS cells into differentiated cells of interest, and hence is expected to be very effective means. However, even with this technique, cell differentiation induction efficiency is low. Accordingly, under the circumstances, it is difficult to obtain a sufficient amount of differentiated cells of interest required for regenerative medicine depending on the kind of cells.

In view of the foregoing, there has been a demand for development of a novel differentiation induction method for producing differentiated cells of interest from pluripotent stem cells more rapidly and more uniformly with higher efficiency.

(Current Situation of Induction of Differentiation of Pluripotent Stem Cells in Related Prior Art)

Non Patent Literatures 1 to 4, which are related art, are each directed to a system for facilitating induction of differentiation of ES/iPS cells. As an example, there is a disclosure that ES/iPS cells are induced into skeletal muscle differentiation.

CITATION LIST Non Patent Literature

-   [NPL 1] Nature medicine 13: 642-648. -   [NPL 2] Cell stem cell 10: 610-619. -   [NPL 3] Mol Ther. November; 20(11): 2153-67. -   [NPL 4] PLoS One. 2013 Apr. 23; 8(4): e61540.

SUMMARY OF INVENTION Problem to be Solved by Invention

In related-art methods of differentiating pluripotent stem cells into a desired cell type, there has not been established a differentiation induction method using human ES/iPS cells and being stable and highly efficient. Many attempts have been made, including a stepwise differentiation induction method based on the control of culture conditions or the addition of, for example, various cell growth factors/differentiation factors to a culture solution, but the use of complicated culture steps is a serious problem. In addition, there are also serious problems in, for example, that the speed of cell differentiation is low, and hence long-period culture is required, and that the differentiation efficiency is low, and hence it is difficult to obtain a sufficient number of required cells.

Means for Solving Problem

The inventors of the present invention have considered that the above-mentioned problems are partly due to the fact that pluripotent stem cells have a property of resisting cell differentiation by various mechanisms (stemness-maintaining property). In view of this, the inventors have found a method of inducing differentiation into a desired cell type within a short period of time and with high efficiency by attenuating differentiation resistance of a pluripotent stem cell to generate a pluripotent stem cell that actively proceeds to a differentiated cell type. Thus, the inventors have completed the present invention.

That is, the present disclosure includes the following.

-   -   1. A differentiation induction kit for differentiating a         pluripotent stem cell into a desired cell type, including at         least any one of the following items (1) to (5):     -   (1) a pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced;     -   (2) a pluripotent stem cell in which a demethylase is forcibly         expressed;     -   (3) a pluripotent stem cell and a demethylase gene;     -   (4) a gene construct carrying a demethylase gene and a         pluripotent stem cell; and     -   (5) a pluripotent stem cell having a gene construct carrying a         demethylase gene inserted into a genome thereof.     -   2. A differentiation induction kit according to the         above-mentioned item 1, wherein the differentiation induction         kit includes the above-mentioned item (1), (2), or (5).     -   3. A differentiation induction kit according to the         above-mentioned item 1 or 2, wherein the demethylase is JMJD3.     -   4. A differentiation induction kit according to the         above-mentioned item 1 or 2, wherein the demethylase is a         demethylase containing only an enzymatically active region of         JMJD3.     -   5. A differentiation induction kit according to the         above-mentioned item 3, wherein the demethylase has an amino         acid sequence set forth in any one of SEQ ID NOS: 1 to 3.     -   6. A differentiation induction kit according to any one of the         above-mentioned items 1 to 5, further including a transcription         factor required for induction of differentiation into the         desired cell type.     -   7. A differentiation induction kit for differentiating a         pluripotent stem cell into a skeletal muscle cell, including at         least any one of the following items (1) to (5):     -   (1) a pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced, and a         transcription factor MYOD1;     -   (2) a pluripotent stem cell in which a demethylase is forcibly         expressed, and a transcription factor MYOD1;     -   (3) a pluripotent stem cell, a demethylase gene, and a         transcription factor MYOD1;     -   (4) a gene construct carrying a demethylase gene, a pluripotent         stem cell, and a transcription factor MYOD1; and     -   (5) a pluripotent stem cell having a gene construct carrying a         demethylase gene inserted into a genome thereof, and a         transcription factor MYOD1.     -   8. A differentiation induction kit for differentiating a         pluripotent stem cell into a nerve cell, including at least any         one of the following items (1) to (5):     -   (1) a pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced, and         transcription factors NEUROG1, NEUROG2, NEUROG3, NEUROD1, and         NEUROD2;     -   (2) a pluripotent stem cell in which a demethylase is forcibly         expressed, and transcription factors NEUROG1, NEUROG2, NEUROG3,         NEUROD1, and NEUROD2;     -   (3) a pluripotent stem cell, a demethylase gene, and         transcription factors NEUROG1, NEUROG2, NEUROG3, NEUROD1, and         NEUROD2;     -   (4) a gene construct carrying a demethylase gene, a pluripotent         stem cell, and transcription factors NEUROG1, NEUROG2, NEUROG3,         NEUROD1, and NEUROD2; and     -   (5) a pluripotent stem cell having a gene construct carrying a         demethylase gene inserted into a genome thereof, and         transcription factors NEUROG1, NEUROG2, NEUROG3, NEUROD1, and         NEUROD2.     -   9. A differentiation induction kit for differentiating a         pluripotent stem cell into a liver cell, including at least any         one of the following items (1) to (5):     -   (1) a pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced, and a         transcription factor HNF1A;     -   (2) a pluripotent stem cell in which a demethylase is forcibly         expressed, and a transcription factor HNF1A;     -   (3) a pluripotent stem cell, a demethylase gene, and a         transcription factor HNF1A;     -   (4) a gene construct carrying a demethylase gene, a pluripotent         stem cell, and a transcription factor HNF1A; and     -   (5) a pluripotent stem cell having a gene construct carrying a         demethylase gene inserted into a genome thereof, and a         transcription factor HNF1A.     -   10. A method of differentiating a pluripotent stem cell into a         desired cell type, including any one of the following steps (1)         to (7):     -   (1) a step of adding a demethylase gene and a transcription         factor required for induction of differentiation into the         desired cell type to a pluripotent stem cell;     -   (2) a step of inserting a gene construct carrying a demethylase         gene and a transcription factor gene required for induction of         differentiation into the desired cell type into a genome of a         pluripotent stem cell;     -   (3) a step of inserting a gene construct carrying a demethylase         gene into a genome of a pluripotent stem cell, followed by         addition of a transcription factor required for induction of         differentiation into the desired cell type to the cell;     -   (4) a step of inserting a gene construct carrying a demethylase         gene and a gene construct carrying a transcription factor         required for induction of differentiation into the desired cell         type into a genome of a pluripotent stem cell;     -   (5) a step of adding a transcription factor required for         induction of differentiation into the desired cell type to a         pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced;     -   (6) a step of adding a transcription factor required for         induction of differentiation into the desired cell type to a         pluripotent stem cell in which a demethylase is forcibly         expressed; and     -   (7) a step of adding a demethylase and a transcription factor         required for differentiation into the desired cell type to a         pluripotent stem cell.     -   11. A method of differentiating a pluripotent stem cell         according to the above-mentioned item 10, wherein the         differentiation induction kit includes the above-mentioned step         (1), (3), (6), or (7).     -   12. A method of differentiating a pluripotent stem cell         according to the above-mentioned item 10 or 11, wherein the         demethylase is JMJD3.     -   13. A method of differentiating a pluripotent stem cell         according to the above-mentioned item 10 or 11, wherein the         demethylase is a demethylase containing only an enzymatically         active region of JMJD3.     -   14. A method of differentiating a pluripotent stem cell into a         skeletal muscle cell, including any one of the following         steps (1) to (7):     -   (1) a step of adding a demethylase gene and a transcription         factor MYOD1 to a pluripotent stem cell;     -   (2) a step of inserting a gene construct carrying a demethylase         gene and a desired transcription factor MYOD1 gene into a genome         of a pluripotent stem cell;     -   (3) a step of inserting a gene construct carrying a demethylase         gene into a genome of a pluripotent stem cell, followed by         addition of a transcription factor MYOD1 to the cell;     -   (4) a step of inserting a gene construct carrying a demethylase         gene and a gene construct carrying a transcription factor MYOD1         into a genome of a pluripotent stem cell;     -   (5) a step of adding a transcription factor MYOD1 to a         pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced;     -   (6) a step of adding a transcription factor MYOD1 to a         pluripotent stem cell in which a demethylase is forcibly         expressed; and (7) a step of adding a demethylase and a         transcription factor MYOD1 to a pluripotent stem cell.     -   15. A method of differentiating a pluripotent stem cell into a         nerve cell, including any one of the following steps (1) to (7):     -   (1) a step of adding a demethylase gene and a transcription         factor NEUROG1, NEUROG2, NEUROG3, NEUROD1, and/or NEUROD2 to a         pluripotent stem cell;     -   (2) a step of inserting a gene construct carrying a demethylase         gene and a desired transcription factor NEUROG1, NEUROG2,         NEUROG3, NEUROD1, and/or NEUROD2 gene into a genome of a         pluripotent stem cell;     -   (3) a step of inserting a gene construct carrying a demethylase         gene into a genome of a pluripotent stem cell, followed by         addition of a transcription factor NEUROG1, NEUROG2, NEUROG3,         NEUROD1, and/or NEUROD2 to the cell;     -   (4) a step of inserting a gene construct carrying a demethylase         gene and a gene construct carrying a transcription factor         NEUROG1, NEUROG2, NEUROG3, NEUROD1, and/or NEUROD2 into a genome         of a pluripotent stem cell;     -   (5) a step of adding a transcription factor NEUROG1, NEUROG2,         NEUROG3, NEUROD1, and/or NEUROD2 to a pluripotent stem cell         having a histone in which H3K27me3 modification has been         substantially removed or reduced;     -   (6) a step of adding a transcription factor NEUROG1, NEUROG2,         NEUROG3, NEUROD1, and/or NEUROD2 to a pluripotent stem cell in         which a demethylase is forcibly expressed; and     -   (7) a step of adding a demethylase and a transcription factor         NEUROG1, NEUROG2, NEUROG3, NEUROD1, and/or NEUROD2 to a         pluripotent stem cell.     -   16. A method of differentiating a pluripotent stem cell into a         liver cell, including any one of the following steps (1) to (7):     -   (1) a step of adding a demethylase gene and a transcription         factor HNF1A to a pluripotent stem cell;     -   (2) a step of inserting a gene construct carrying a demethylase         gene and a desired transcription factor HNF1A gene into a genome         of a pluripotent stem cell;     -   (3) a step of inserting a gene construct carrying a demethylase         gene into a genome of a pluripotent stem cell, followed by         addition of a transcription factor HNF1A to the cell;     -   (4) a step of inserting a gene construct carrying a demethylase         gene and a gene construct carrying a transcription factor HNF1A         into a genome of a pluripotent stem cell;     -   (5) a step of adding a transcription factor HNF1A to a         pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced;     -   (6) a step of adding a transcription factor HNF1A to a         pluripotent stem cell in which a demethylase is forcibly         expressed; and     -   (7) a step of adding a demethylase and a transcription factor         HNF1A to a pluripotent stem cell.     -   17. A method of differentiating a pluripotent stem cell         according to any one of the above-mentioned items 10 to 13,         wherein the transcription factor required for induction of         differentiation into the desired cell type is TCF-1, and the         desired cell type is a hepatoblast.     -   18. A method of differentiating a pluripotent stem cell         according to any one of the above-mentioned items 10 to 13,         wherein the transcription factor required for induction of         differentiation into the desired cell type is SOX9, and the         desired cell type is a chondrocyte.     -   19. A method of differentiating a pluripotent stem cell         according to any one of the above-mentioned items 10 to 13,         wherein the transcription factor required for induction of         differentiation into the desired cell type is RUNX3, and the         desired cell type is an osteoblast.

Advantageous Effects of Invention

The method of differentiating a pluripotent stem cell into a desired cell type with high efficiency and differentiation induction kit for differentiating a pluripotent stem cell into a desired cell type with high efficiency of the present disclosure have at least any one of the following effects.

(1) The period of time required for cell differentiation starting with the pluripotent stem cell is shortened and/or the differentiation induction efficiency is improved. (2) As modified synthetic mRNA for a gene is used to introduce the gene into the pluripotent stem cell, the introduced gene is not integrated into the genome of the pluripotent stem cell, with the result that there is no risk of canceration or the like after cell differentiation induction. (3) In the introduction of the gene into the pluripotent stem cell using the modified synthetic mRNA, the timing and number of times of the addition of the mRNA for the gene can be easily changed, and hence optimal conditions specific to each of various desired cell types can be selected so as to differentiate the pluripotent stem cell into the desired cell types.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A: A schematic diagram of a method of attenuating differentiation resistance of a pluripotent stem cell to a desired cell type of the present disclosure. FIG. 1B: When H3K27me3 in a human ES or iPS cell is attenuated or removed, a transcription factor (TF) binds to the promoter site of a downstream gene to enhance the expression of a group of development/differentiation-related genes, resulting in differentiation. FIG. 1C: A method of inducing differentiation of a human ES cell or an iPS cell by introducing modified synthetic mRNA for a demethylase, and then introducing modified synthetic mRNA for the transcription factor (TF). FIG. 1D: A method of inducing differentiation of a human ES cell or an iPS cell by simultaneously introducing the modified synthetic mRNAs for the demethylase and the transcription factor (TF).

FIG. 2: A schematic view of a differentiation induction method using modified synthetic mRNA for a target gene.

FIG. 3: A schematic view of a differentiation step using modified synthetic mRNA for a target gene.

FIG. 4: A method of introducing a target gene into the genome of a pluripotent stem cell.

FIGS. 5A-5H: The generation of H3K27me3-attenuated hESCs by JMJD3c expression. FIG. 5A: The structures of full-length JMJD3 (JMJD3f) and JMJD3c proteins. JMJD3c was designed to contain the JmjC domain (amino acids 1376 to 1484) having demethylase activity. FIG. 5B: hESCs were transfected with modified synthetic mRNA for human influenza virus hemagglutinin (HA)-tagged full-length JMJD3 (HA-JMJD3f) or HA-tagged JMJD3c (HA-JMJD3c), and were stained with an anti-HA antibody and an anti-H3K27me3 antibody. The arrowheads indicate the transfected cells.

FIG. 5C: The effects of transfection of the HA-JMJD3f and HA-JMJD3c mRNAs on H3K27me3 were analyzed by an immunoblotting method. Modified synthetic mRNA for a green fluorescent protein Emerald (Em) was transfected as a control. An anti-H3 antibody was used as a loading control. FIG. 5D: A plasmid vector for tet-on induction of JMJD3c in hESCs (JMJD3c-hESCs). FIG. 5E: JMJD3c-hESCs were stained with 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal) 3 days after doxycycline (Dox) treatment. FIG. 5F: HA-JMJD3c-induced H3K27me3 demethylation was detected 1 day to 3 days after DOX treatment.

FIG. 5G: A point mutation in a JMJD3c mutant (mut) was introduced at amino acid 1390 for demethylase inactivation. FIG. 5H: Confirmation of the influences of HA-JMJD3c and HA-JMJD3c mut on H3K27me3.

FIGS. 6A-6C: Development/differentiation-related genes whose gene expression are upregulated in JMJD3-hESCs. FIG. 6A: Morphologies of JMJD3-hESCs without Dox treatment (−JMJD3c) and with Dox treatment (+JMJD3c). FIG. 6B: Changes in H3K27me3 and H3K4me3 after Dox treatment (Day 0 to Day 3) were analyzed by ChIP-qPCR. POU5F1 and NANOG are stem cell genes, and T, MX1, SOX17, FOXA2, GATA4, GATA6, GSC, and EVX1 are mesendodermal differentiation-related genes. n=2 or 3. *P<0.05. The error bars indicate the standard error of the mean (SEM). FIG. 6C: qRT-PCR analyses for showing relative expression of stem cell genes and mesendodermal differentiation-related genes under differentiation conditions as compared with hESCs. Basal Medium represents a medium without cytokines and growth factors, activin A represents a medium for endodermal differentiation, activin A+BMP4+bFGF represents a medium for mesodermal differentiation, and JMJD3c represents a medium with Dox (forced expression of JMJD3c). The expression levels were normalized to the expression amount of glyceraldehyde 3-phosphate dehydrogenase (GAPDH).

FIGS. 7A-7G: JMJD3c facilitates MYOD1-mediated muscle differentiation of hESCs. FIG. 7A: A schematic of a differentiation protocol. JMJD3c-hESCs were treated with or without Dox on from Day 1 to Day 2 after plating and were transfected with synthetic mRNA for MYOD1 or Emerald three times on from Day 2 to Day 3. The cells were collected on Day 5. FIG. 7B: RT-qPCR analyses of muscle differentiation-related genes in MYOD1-differentiated cells with Dox treatment (+JMJD3c) or without Dox treatment (−JMJD3c). − represents no transfection, Em represents Emerald transfection, and MYOD1 represents MYOD1 transfection. The expression levels were normalized to GAPDH. n=3. The error bars indicate the SEM. FIG. 7C: ChIP-qPCR analyses of H3K27me3, H3K4me3, and H3K27ac in the promoter regions of MYOG and MEF2C genes of MYOD1-transfected cells with Dox treatment (+JMJD3c) or without Dox treatment (−JMJD3c). For the promoter regions of the MYOG and MEF2C genes, two regions (FIGS. 7A to 7C) and three regions (FIG. 7A, 7B) were tested, respectively. GAPDH, POU5F1, and T each represent a positive control, and SOX1 represents a negative control. n=2 or 3. P<0.05. The error bars indicate the SEM. FIG. 7D: Immunostaining for myosin heavy chain isoform (MHC) in the cells in which JMJD3c, MYOD1, or JMJD3c+MYOD1 are forcibly expressed. FIG. 7E: The percentage of nuclei contained within MHC-stained cells. n=3. *P<0.01. The error bars indicate SEM. FIG. 7F: Immunostaining for MHC in the MYOD1-transfected cells in which JMJD3c or the JMJD3c mutant is forcibly expressed. FIG. 7G: The percentage of nuclei contained within MHC-stained cells. n=3. *P<0.01. The error bars indicate the SEM. FIGS. 8A-8G: Differentiation of hESCs and iPSCs into skeletal muscle cells by transfection of a demethylase and a transcription factor as synthetic mRNAs. FIG. 8A: A schematic of a differentiation induction protocol. hESC/iPSCs were transfected with synthetic mRNAs for JMJD3c or a red fluorescent protein mCherry twice on Day 1 and Day 2 and MYOD1 three times on Day 2 and Day 3. The cells were fixed for immunostaining on Day 5. FIG. 8B: Immunostaining for MHC in cells that were transfected with MYOD1 after mCherry or JMJD3c transfection. FIG. 8C: The percentage of nuclei contained within MHC-stained cells. n=3. *P<0.01. The error bars indicate the SEM. FIG. 8D: Representative staining images for showing muscular fusion (arrowheads). FIG. 8E: Induced myogenic cells were labeled with green fluorescence and cocultured with mouse C2C12 cells having nuclei labeled with red fluorescence. On Day 3 and Day 5 after coculturing, cell fusions were detected (arrowheads). FIG. 8F: iPSCs were transfected with mCherry or JMJD3c, followed by MYOD1, and were immunostained for MHC. FIG. 8G: The percentage of nuclei contained within MHC-stained cells. n=3. *P<0.01. The error bars indicate the SEM.

FIG. 9: Increases in expression of marker genes for hepatoblasts (TCF-1), chondrocytes (SOX9), and osteoblasts (RUNX3) through expression of respective transcription factors TCF-1, SOX9, and RUNX3 in combination with JMJD3c. AFP is a marker gene for hepatoblasts, COL2 is a marker gene for chondrocytes, and COL1A1 is a marker gene for osteoblasts. The expression levels were standardized to GAPDH. n=2. *P<0.05. The error bars indicate the SEM.

DESCRIPTION OF EMBODIMENTS

A method of inducing differentiation of a pluripotent stem cell into a desired cell type with high efficiency of the present disclosure (hereinafter sometimes referred to as “method of the present disclosure”) is described below, though the method is not particularly limited as long as the method can attenuate differentiation resistance of a pluripotent stem cell to the desired cell type.

(Pluripotent Stem Cell)

The pluripotent stem cell to be used in the method of the present disclosure is not particularly limited, but is preferably derived from a mammal, more preferably derived from a human. The pluripotent stem cell is, for example, a human ES cell, a human iPS cell, or any combination thereof, is not particularly limited, and encompasses tissue stem cells derived from tissues and organs, dermal fibroblasts, and all kinds of cells derived from tissues or organs.

(Attenuating Differentiation Resistance of Pluripotent Stem Cell to Desired Cell Type)

In pluripotent stem cells, a special chromatin structure called a “bivalent domain” is formed in each promoter region of a group of genes involved in differentiation, and under a stemness-maintaining state, the group of genes involved in development/differentiation are in a standby state so as not to be easily expressed. In Examples of the present disclosure, it has been confirmed that “when a methyl group modification of a histone called H3K27me3 is removed or reduced in the “bivalent domain”, the expression of differentiation genes required for induction of differentiation into the desired cell type is rapidly and efficiently facilitated” (see FIGS. 1A-1D).

That is, the “attenuating differentiation resistance of a pluripotent stem cell to a desired cell type” of the present disclosure means that the H3K27me3 modification of the pluripotent stem cell is substantially removed or reduced.

In addition, a state in which the H3K27me3 modification of the pluripotent stem cell has been substantially removed or reduced may be confirmed by a comparison to the degree of the H3K27me3 modification of a pluripotent stem cell that has not been subjected to the removing or the reducing. For example, the state (degree) in which the H3K27me3 modification of the pluripotent stem cell has been substantially removed or reduced is from 95 to 1, from 90 to 2, from 85 to 3, from 80 to 4, from 75 to 5, from 70 to 6, from 65 to 7, from 60 to 8, from 50 to 10, from 40 to 20, about 30, or 50 or less, 40 or less, 30 or less, 20 or less, or 10 or less when compared to the degree of the H3K27me3 modification of the pluripotent stem cell that has not been removed or reduced, which is defined as 100. The degree of the H3K27me3 modification of the pluripotent stem cell may be easily measured by using a commercially available anti-Histone H3K27me3 antibody, and the gene expression amount of H3K27me3 may be measured by a method known per se.

(Method of inducing Differentiation of Pluripotent Stem Cell into Desired Cell Type with High Efficiency of the Present Disclosure)

As described above, the method of the present disclosure is not particularly limited as long as the method can attenuate differentiation resistance of the pluripotent stem cell to the desired cell type, and may be exemplified by the following.

(Use of Modified Synthetic mRNA for Target Gene)

The method of the present disclosure includes adding (introducing, transfecting), to a pluripotent stem cell, a gene for a compound having an action of substantially removing or reducing H3K27me3 modification, and a gene for a transcription factor required for induction of differentiation of the pluripotent stem cell into the desired cell type.

The term “gene” as used herein encompasses not only double strands, but also their respective constituent single strands, such as plus strands (or sense strands) or complementary strands (or antisense strands), linear nucleic acids, and circular nucleic acids, and encompasses DNA, RNA, mRNA, cDNA, and the like, unless otherwise stated.

In addition, the term “target gene” is meant to encompass both or any one of the gene for the compound having an action of substantially removing or reducing H3K27me3 modification and the transcription factor required for induction of differentiation into the desired cell type.

In a step of the method of the present disclosure, a method known per se may be used without any particular limitation as a method of adding (introducing, transfecting) the gene for the compound having an action of substantially removing or reducing H3K27me3 modification and/or the transcription factor required for induction of differentiation into the desired cell type to the pluripotent stem cell. There is preferably used a method of inducing differentiation by efficiently introducing synthetic mRNA for a transcription factor into human pluripotent stem cells through use of a gene expression method involving using synthetic mRNA developed by Warren, Rossi, et al. (reference: Cell Stem Cell 7: 618-630, 2010.), which is a footprint-free forced gene expression method causing no gene integration into a host genome (see FIG. 2).

The timing at which the gene for the compound having an action of substantially removing or reducing H3K27me3 modification and the transcription factor required for induction of differentiation into the desired cell type are added to the pluripotent stem cell is not particularly limited, but it is preferred that the gene for the compound having an action of substantially removing or reducing H3K27me3 modification be added to the pluripotent stem cell before the addition of the transcription factor required for differentiation induction.

Further, with regard to the addition timing of each gene (mRNA), the addition may be performed, for example, one or more times, preferably two to five times, two to four times, two or three times, or two times every 12 hours to 64 hours, but the addition timing is not particularly limited thereto.

A more specific method may be exemplified by the following. (Synthesis of Modified mRNA encoding Amino Acid Sequence of Transcription Factor)

Modified mRNA is synthesized with reference to a method described in the literature “Warren et al., Cell Stem Cell, 2010 Nov. 5; 7 (5): 618-30.” More detailed, mRNA is synthesized by in vitro transcription using a mixture of dNTPs (dNTPs: 3-0-Me-m7G (5′)ppp(5′)GARCA cap analog, 5-methylcytidine triphosphate, and pseudouridine triphosphate) obtained by modifying template DNA encoding the amino acid sequence of the transcription factor required for induction of differentiation into the desired cell type.

(Generation of Sendai Virus Vector encoding Amino Acid Sequence of Transcription Factor)

In order to express a mammalian (in particular, human) transcription factor, a Sendai virus vector capable of expressing a human transcription factor is preferably used. In particular, a mutant of a Sendai virus vector, such as an F protein-deficient mutant, has no infectivity, and is easy to handle (see Inoue et al., J Virol. 77: 23238-3246, 2003).

(Method of inducing Differentiation of Pluripotent Stem Cell into Desired Cell Type with High Efficiency)

A single transcription factor or a cocktail of two or more transcription factors required for induction of differentiation into the desired cell type is prepared. The form of the transcription factors is not particularly limited, and may be any of synthetic mRNAs, a Sendai virus vector having incorporated therein a transcription factor (or a plurality of transcription factors), and nanoparticle capsules containing synthetic mRNAs.

A method of introducing the single transcription factor or cocktail of two or more transcription factors described above into cells is not particularly limited, and transfection with Lipofectamine, viral infection, or the like is utilized. A schematic view of the differentiation induction step of the method of the present disclosure is illustrated in FIG. 3.

(Use of Expression Vector)

In a step of the method of the present disclosure, an expression vector known per se having introduced therein the gene for the compound having an action of substantially removing or reducing H3K27me3 modification and/or the transcription factor required for induction of differentiation into the desired cell type may be used. Examples of the expression vector to be used in the present disclosure may include, but not particularly limited to, an animal cell expression plasmid vector and a Sendai virus vector.

A method of introducing the synthetic mRNA and the expression vector into the pluripotent stem cell is not particularly limited, for examples thereof may include a lipofection method, a liposome method, an electroporation method, a calcium phosphate coprecipitation method, a diethylaminoethyl (DEAE)-dextran method, a microinjection method, and a gene gun method. A particularly preferred example is a lipofection method.

Another method may involve using an expression vector for the gene for the compound having an action of substantially removing or reducing H3K27me3 modification, and using synthetic mRNA for the transcription factor required for induction of differentiation into the desired cell type, or may adopt the opposite pattern.

(Compound having Action of substantially removing or reducing H3K27Me3 Modification)

The compound having an action of substantially removing or reducing H3K27me3 modification of the present disclosure is not particularly limited, and is, for example, a demethylase (in particular, a demethylase having an action of removing a methyl group of H3K27me3), an antibody that specifically binds to H3K27me3, an antibody for a Polycomb-group proteins (PcG proteins) having an H3K27me3 modification action, small interfering RNA (siRNA), or an inhibitor.

In addition, not only by using those compounds alone, but also by using a plurality of kinds of compounds and/or a low-molecular-weight compound in combination, it is possible to efficiently “attenuate differentiation resistance of a pluripotent stem cell to a desired cell type (substantially remove or reduce H3K27me3 modification of a pluripotent stem cell).”

Examples of the low-molecular-weight compound may include, but not particularly limited to, histone deaceylase (HDAC) inhibitors, such as valproic acid.

Examples of the demethylase include AOF (LSD1), AOF1 (LSD2), FBXL11 (JHDM1A), Fbxl10 (JHDM1B), FBXL19 (JHDM1C), KIAA1718 (JHDM1D), PHF2 (JHDM1E), PHF8 (JHDM1F), JMJD1A(JHDM2A), JMJD1B(JHDM2B), JMJD1C (JHDM2C), JMJD2A (JHDM3A), JMJD2B (JHDM3B), JMJD2C (JHDM3C), JMJD2D (JHDM3D), RBP2 (JARID1A), PLU1 (JARID1B), SMCX (JARID1C), SMCY (JARID1D), Jumonji (JARID2), UTX(UTX), UTY(UTY), JMJD3 (JMJD3), JMJD4 (JMJD4), JMJD5(JMJD5), JMJD6(JMJD6), JMJD7(JMJD7), and JMJD8(JMJD8). Of those, JMJD3 or the like is preferred as a demethylase having an action of removing a methyl group of H3K27me3.

In addition, the demethylase of the present disclosure may also include the following:

-   -   (1) a protected derivative, sugar chain-modified product,         acylated derivative, or acetylated derivative of any one of the         demethylases described above;     -   (2) an enzyme that has 90% (or 92%, 94%, 96%, 98%, or 99%) or         more homology to any one of the demethylases described above and         has a substantially equivalent action of substantially removing         or reducing H3K27me3 modification to that of the demethylase;         and     -   (3) an enzyme that has 100 to 10, 50 to 30, 40 to 20, 10 to 5,         or 5 to 1 amino acid substituted, deleted, inserted, and/or         added in any one of the demethylases described above and has a         substantially equivalent action of substantially removing or         reducing H3K27me3 modification to that of the demethylase.

Further, the gene of the demethylase of the present disclosure includes the following:

-   -   (1) a gene encoding a polypeptide formed of the amino acid         sequence of any one or more of the enzymes described above;     -   (2) a gene encoding a polypeptide that has 1 to 20 (or 1 to 15,         1 to 10, 1 to 7, 1 to 5, or 1 to 3) amino acids substituted,         deleted, inserted, and/or added in the amino acid sequence of         any one or more of the enzymes described above and has a         substantially equivalent action of substantially removing or         reducing H3K27me3 modification to that of the demethylase; and     -   (3) a gene encoding a polypeptide that has 90% (or 92%, 94%,         96%, 98%, or 99%) or more homology to the amino acid sequence of         any one or more of the enzymes described above and has a         substantially equivalent action of substantially removing or         reducing H3K27me3 modification to that of the demethylase.

An enzyme having a mutation may be a naturally occurring one, or may be one obtained by introducing a mutation on the basis of a gene of natural origin. Means for introducing a mutation is known per se, and for example, a site-directed mutagenesis method, a homologous gene recombination method, a primer extension method, a polymerase chain reaction (hereinafter abbreviated as PCR), and the like may be used alone or in combination thereof as appropriate.

The method may be performed in conformity with any of methods described in the literatures (“Molecular Cloning: A Laboratory Manual, second edition” edited by Sambrook et al., 1989, Cold Spring Harbor Laboratory; and “Lab Manual: Genetic Engineering” edited by Masami Muramatsu, 1988, Maruzen), or by modifying these methods, and Ulmer's technology (Ulmer, K. M., “Science”, 1983, volume 219, p. 666-671) may also be utilized. In the case of a peptide, from the viewpoint of preventing alteration of basic properties of the peptide (e.g., physical properties, function, physiological activity, or immunological activity) in the introduction of a mutation, for example, mutual substitution between homologous amino acids (e.g., polar amino acids, non-polar amino acids, hydrophobic amino acids, hydrophilic amino acids, positively charged amino acids, negatively charged amino acids, and aromatic amino acids) is easily conceivable.

(JMJD3)

JMJD3 is known as a demethylase for H3K27me3 of a histone (mouse NP 001017426, human NP 001073893), and even in its full length (NP 001073893, SEQ ID NO: 1), has an action of substantially removing or reducing the H3K27me3 modification of pluripotent stem cells. However, in Example 1 of the present disclosure, it has been confirmed that JMJD3c having the JmjC domain {SEQ ID NO: 2, catalytic domain: SEQ ID NO: 3 (amino acids 1376-1484)} has a stronger action of substantially removing or reducing H3K27me3 modification as compared to full-length JMJD3 (see Example 2).

In addition, the JMJD3 of the present disclosure encompasses the following embodiments as well:

-   -   (1) a protected derivative, sugar chain-modified product,         acylated derivative, or acetylated derivative of an amino acid         sequence set forth in SEQ ID NO: 1;     -   (2) an amino acid sequence that has 90% (or 92%, 94%, 96%, 98%,         or 99%) or more homology to the amino acid sequence set forth in         SEQ ID NO: 1 and has a substantially equivalent action of         substantially removing or reducing H3K27me3 modification to that         of the JMJD3;     -   (3) an amino acid sequence that has 100 to 10, 50 to 30, 40 to         20, 10 to 5, or 5 to 1 amino acid substituted, deleted,         inserted, and/or added in the amino acid sequence set forth in         SEQ ID NO: 1 and has a substantially equivalent action of         substantially removing or reducing H3K27me3 modification to that         of the JMJD3;     -   (4) a protected derivative, sugar chain-modified product,         acylated derivative, or acetylated derivative of an amino acid         sequence set forth in SEQ ID NO: 2;     -   (5) an amino acid sequence that has 90% (or 92%, 94%, 96%, 98%,         or 99%) or more homology to the amino acid sequence set forth in         SEQ ID NO: 2 and has a substantially equivalent action of         substantially removing or reducing H3K27me3 modification to that         of the JMJD3c;     -   (6) an amino acid sequence that has 100 to 10, 50 to 30, 40 to         20, 10 to 5, or 5 to 1 amino acid substituted, deleted,         inserted, and/or added in the amino acid sequence set forth in         SEQ ID NO: 2 and has a substantially equivalent action of         substantially removing or reducing H3K27me3 modification to that         of the JMJD3c;     -   (7) a protected derivative, sugar chain-modified product,         acylated derivative, or acetylated derivative of an amino acid         sequence set forth in SEQ ID NO: 3;     -   (8) an amino acid sequence that has 90% (or 92%, 94%, 96%, 98%,         or 99%) or more homology to the amino acid sequence set forth in         SEQ ID NO: 3 and has a substantially equivalent action of         substantially removing or reducing H3K27me3 modification to that         of the JMJD3;     -   (9) an amino acid sequence that has 100 to 10, 50 to 30, 40 to         20, 10 to 5, or 5 to 1 amino acid substituted, deleted,         inserted, and/or added in the amino acid sequence set forth in         SEQ ID NO: 3 and has a substantially equivalent action of         substantially removing or reducing H3K27me3 modification to the         JMJD3; and     -   (10) an amino acid sequence that includes the amino acid         sequence set forth in SEQ ID NO: 3 and has a substantially         equivalent action of substantially removing or reducing H3K27me3         modification to the JMJD3c.

It is appropriate that the “sequence homology” be generally 70% or more, preferably 80%, more preferably 85% or more, still more preferably 90% or more, even more preferably 95% or more, most preferably 98% or more of an entire amino acid sequence.

Further, the JMJD3 gene of the present disclosure encompasses the following:

-   -   (1) a gene encoding a polypeptide formed of an amino acid         sequence set forth in any one of SEQ ID NOS: 1 to 3;     -   (2) a gene encoding a polypeptide that has 1 to 20 (or 1 to 15,         1 to 10, 1 to 7, 1 to 5, or 1 to 3) amino acids substituted,         deleted, inserted, and/or added in the amino acid sequence set         forth in any one of SEQ ID NOS: 1 to 3 and has a substantially         equivalent action of substantially removing or reducing H3K27me3         modification to that of the amino acid sequence set forth in any         one of SEQ ID NOS: 1 to 3;     -   (3) a gene encoding a polypeptide that has 90% (or 92%, 94%,         96%, 98%, or 99%) or more homology to the amino acid sequence         set forth in any one of SEQ ID NOS: 1 to 3 and has a         substantially equivalent action of substantially removing or         reducing H3K27me3 modification to that of the amino acid         sequence set forth in any one of SEQ ID NOS: 1 to 3;     -   (4) a gene formed of a base sequence set forth in any one of SEQ         ID NOS: 4 to 6;     -   (5) a gene encoding a polypeptide that hybridizes with a base         sequence complementary to the base sequence set forth in any one         of SEQ ID NOS: 4 to 6 under stringent conditions and has a         substantially equivalent action of substantially removing or         reducing H3K27me3 modification to that of the amino acid         sequence set forth in any one of SEQ ID NOS: 1 to 3;     -   (6) a gene that has a sequence of 1 to 50 (or 1 to 40, 1 to 30,         1 to 20, 1 to 15, 1 to 10, 1 to 5, or 1 to 3 bases substituted,         deleted, inserted, and/or added in the gene (DNA) formed of the         base sequence set forth in any one of SEQ ID NOS: 4 to 6; and     -   (7) a gene having 90% (or 92%, 94%, 96%, 98%, or 99%) or more         homology to the gene formed of the base sequence set forth in         any one of SEQ ID NOS: 4 to 6.

(Transcription Factor required for Highly Efficient Induction of Differentiation into Desired Cell Type)

The form of the “transcription factor required for highly efficient induction of differentiation into the desired cell type” to be used in the method of the present disclosure is not particularly limited, for examples thereof may include, but not particularly limited to, nucleic acids, such as RNA and DNA, synthetic nucleic acids, and proteins. The following examples may be given.

In addition, in the method of the present disclosure, examples of the desired cell type may include a skeletal muscle (skeletal muscle cells), the liver (liver cells), and nerve (nerve cells).

{Transcription Factor required for Induction of Differentiation into Skeletal Muscle (in particular, Cells present in Skeletal Muscle)}

A method of inducing differentiation into a skeletal muscle is as described below.

A single transcription factor, or two or more transcription factors selected from the group consisting of MYOD1, NRF1, SALL4, ZIC1, KLF9, ZNF281, CTCF, HES1, HOXA2, TBX5, TP73, ERG, MAB21L3, PRDM1, NFIC, CTCFL, FOXP1, HEY1, PITX2, JUNB, KLF4, ESX1, TFAP2C, FOS, TFE3, FOSL1, GRHL2, TBX2, NFIB, and IRF4 are introduced into a pluripotent stem cell having a histone in which H3K27me3 modification has been substantially removed or reduced.

In particular, the JMJD3c gene (SEQ ID NO: 80) and MYOD1 (myogenic differentiation 1: SEQ ID NO: 86, SEQ ID NO: 88) are added to pluripotent stem cells known per se.

{Transcription Factor required for Induction of Differentiation into Liver (in particular, Cells present in Liver, i.e., Liver Cells or Hepatoblasts)}

A method of inducing differentiation into the liver (in particular, the liver, liver cells, or the fetal liver) is as described below.

Liver: A single transcription factor, or two or more transcription factors selected from TCF-1, SALL4, TGIF1, MAB21L3, ZIC1, EGFLAM, PITX2, HNF4A, NRF1, ZNF281, CTCFL, TP73, TFE3, DLX6, and TCF4 are introduced into human pluripotent stem cells.

Fetal liver: A single transcription factor, or two or more transcription factors selected from TCF-1, SIX5, HNF4A, SIN3A, ID1, and HNF1A are introduced into human pluripotent stem cells.

In particular, the JMJD3c gene (SEQ ID NO: 80) and HNF1A (hepatocyte nuclear factor 1, alpha: SEQ ID NO: 87, SEQ ID NO: 94) are added to pluripotent stem cells known per se.

{Transcription Factor required for Induction of Differentiation into Neural Cells (in particular, Motoneurons or Peripheral Motoneuron Cells)}

A method of inducing differentiation into neural cells (in particular, motoneurons or peripheral motoneuron cells) is as described below.

A single transcription factor, or two or more, three or more, or four or more transcription factors selected from NEUROG1 (neurogenin 1: SEQ ID NO: 81), NEUROG2 (neurogenin 2: SEQ ID NO: 82), NEUROG3 (neurogenin 3: SEQ ID NO: 83), NEUROD1 (neurogenic differentiation 1: SEQ ID NO: 84), and NEUROD2 (neurogenic differentiation 2: SEQ ID NO: 85) or all of these transcription factors are introduced into human pluripotent stem cells.

In particular, the JMJD3c gene (SEQ ID NO: 80), and NEUROG1 (SEQ ID NO: 81, SEQ ID NO: 89), NEUROG2 (SEQ ID NO: 82, SEQ ID NO: 90), NEUROG3 (SEQ ID NO: 83, SEQ ID NO: 91), NEUROD1 (SEQ ID NO: 84, SEQ ID NO: 92), and NEUROD2 (SEQ ID NO: 85, SEQ ID NO: 93) are added to pluripotent stem cells known per se.

(Method of introducing Target Gene into Genome of Pluripotent Stem Cell)

In a step of the method of the present disclosure, a method known per se may be used without any particular limitation as a method of introducing the gene for the compound having an action of substantially removing or reducing H3K27me3 modification and/or the transcription factor required for highly efficient induction of differentiation into the desired cell type into the genome of the pluripotent stem cell. There may be preferably used an expression cassette inserted between PiggyBac transposase recognition sequences (PB sequences) developed by Woltjen et al. (reference: Nature 458: 766-770, 2009.), which is a mechanism by which a gene to be introduced is actively incorporated into pluripotent stem cells (in particular, the genome of human ES cells). The expression cassette is a system capable of efficiently establishing a genetically modified pluripotent stem cell line by introducing a drug selection cassette (see FIG. 4).

(Method of introducing Target Protein into Pluripotent Stem Cell)

In a step of the method of the present disclosure, a method known per se may be used as a method of introducing the compound (in particular, protein) having an action of substantially removing or reducing H3K27me3 modification and/or the transcription factor (protein) required for highly efficient induction of differentiation into the desired cell type into the genome of the pluripotent stem cell, and examples thereof may include: a method involving using a protein transfection reagent; a method involving using a fusion protein having added thereto a cell-penetrating peptide; and a microinjection method.

The “cell membrane permeable peptide” of the present disclosure is a peptide having a property of migrating into a cell, more specifically a property of permeating a cell membrane, still more specifically a property of permeating a cell membrane or a nuclear membrane to permeate into cytoplasm or a nucleus. The amino acid sequence of the peptide is not particularly limited, but examples thereof may include TAT (GRKKRRQRRRPQ: SEQ ID NO: 7), r8 {rrrrrrrr (D-form-R): SEQ ID NO: 8}, and MPG-8 ((3AFLGWLGAWGTMGWSPKKKRK: SEQ ID NO: 9).

The target protein encompasses both of the compound (in particular, protein) having an action of substantially removing or reducing H3K27me3 modification and/or the transcription factor (protein) required for highly efficient induction of differentiation into the desired cell type.

(Differentiation Induction Kit for inducing Differentiation of Pluripotent Stem Cell into Desired Cell Type with High Efficiency)

A differentiation induction kit for inducing differentiation of a pluripotent stem cell into a desired cell type with high efficiency of the present disclosure (hereinafter sometimes referred to as “kit of the present disclosure”) includes any one or more of the following embodiments.

(1) Pluripotent Stem Cell in which H3K27me3 Modification has been substantially removed or reduced

A pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced can be easily generated by the method of the present disclosure described above.

A practitioner of the present disclosure can easily induce differentiation into the desired cell type by introducing the transcription factor required for induction of differentiation into the desired cell type as described above into the pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced.

In addition, the pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced encompasses a pluripotent stem cell having a gene construct inducible with doxycycline or the like inserted into the genome thereof so that a demethylase can be transiently forcibly expressed therein.

(2) Demethylase Gene for Kit of the Present Disclosure

A practitioner of the present disclosure can easily generate the pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced by adding a demethylase gene for a kit to a pluripotent stem cell known per se.

Examples of the demethylase gene for a kit may include, but not particularly limited to, mRNAs, DNAs, and proteins of demethylase genes (e.g., JMJD3c).

(3) Demethylase Gene for Kit and Gene containing Transcription Factor required for Induction of Differentiation into Desired Cell Type of the Present Disclosure.

A practitioner of the present disclosure can easily generate the pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced, and induce differentiation into the desired cell type with high efficiency by adding the demethylase gene for a kit and a gene containing the transcription factor required for induction of differentiation into the desired cell type to a pluripotent stem cell known per se.

The two genes may be present on one gene, or on separate genes. When the two genes are present on separate genes, the demethylase gene and the transcription factor required for induction of differentiation into the desired cell type may be added to the pluripotent stem cell simultaneously or at separate times.

(4) Demethylase for Kit of the Present Disclosure

A practitioner of the present disclosure can easily generate the pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced by adding a demethylase for a kit to a pluripotent stem cell known per se.

(5) Gene Construct carrying Demethylase Gene of the Present Disclosure

A practitioner of the present disclosure can easily generate the pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced by introducing a gene construct carrying a demethylase gene into the genome of a pluripotent stem cell known per se.

The gene construct may contain a promoter sequence, a gene expression-enhancing sequence, a marker gene, a reporter sequence, a drug resistance gene, and the like as required in addition to the demethylase gene.

(6) Gene Construct carrying Demethylase Gene and Transcription Factor required for Induction of Differentiation into Desired Cell Type of the Present Disclosure

A practitioner of the present disclosure can easily generate the pluripotent stem cell in which H3K27me3 modification has been substantially removed or reduced, and induce differentiation into the desired cell type by introducing a gene construct carrying a demethylase gene and a transcription factor required for induction of differentiation into the desired cell type into the genome of a pluripotent stem cell known per se.

The two genes may be present on one gene, or on separate genes. When the two genes are present on separate genes, the demethylase gene and the transcription factor required for induction of differentiation into the desired cell type may be introduced into the genome of the pluripotent stem cell simultaneously or at separate times.

The gene construct may contain a promoter sequence, a gene expression-enhancing sequence, a marker gene, a reporter sequence, a drug resistance gene, and the like as required in addition to the demethylase gene and the transcription factor required for induction of differentiation into the desired cell type.

A method of differentiating a pluripotent stem cell into a desired cell type of the present disclosure may be exemplified by, but not particularly limited to, a method including any one of the following steps (1) to (7):

-   -   (1) a step of adding a demethylase gene and a transcription         factor required for induction of differentiation into the         desired cell type to a pluripotent stem cell;     -   (2) a step of inserting a gene construct carrying a demethylase         gene and a transcription factor gene required for induction of         differentiation into the desired cell type into a genome of a         pluripotent stem cell;     -   (3) a step of inserting a gene construct carrying a demethylase         gene into a genome of a pluripotent stem cell, followed by         addition of a transcription factor required for induction of         differentiation into the desired cell type to the cell;     -   (4) a step of inserting a gene construct carrying a demethylase         gene and a gene construct carrying a transcription factor         required for induction of differentiation into the desired cell         type into a genome of a pluripotent stem cell;     -   (5) a step of adding a transcription factor required for         induction of differentiation into the desired cell type to a         pluripotent stem cell having a histone in which H3K27me3         modification has been substantially removed or reduced;     -   (6) a step of adding a transcription factor required for         induction of differentiation into the desired cell type to a         pluripotent stem cell in which a demethylase is forcibly         expressed; and     -   (7) a step of adding a demethylase and a transcription factor         required for differentiation into the desired cell type to a         pluripotent stem cell.

The present disclosure also encompasses any one of the following pluripotent stem cells for differentiation into a desired cell type:

-   -   (1) a pluripotent stem cell for differentiation into a desired         cell type, which has a histone in which H3K27me3 modification         has been substantially removed or reduced;     -   (2) a pluripotent stem cell for differentiation into a desired         cell type, in which a demethylase is forcibly expressed; and     -   (3) a pluripotent stem cell for differentiation into a desired         cell type, which has a gene construct carrying a demethylase         gene inserted into the genome thereof.

The present disclosure also encompasses a use of any one of the following pluripotent stem cells for differentiation into a desired cell type:

-   -   (1) a pluripotent stem cell for differentiation into a desired         cell type, which has a histone in which H3K27me3 modification         has been substantially removed or reduced;     -   (2) a pluripotent stem cell for differentiation into a desired         cell type, in which a demethylase is forcibly expressed; and     -   (3) a pluripotent stem cell for differentiation into a desired         cell type, which has a gene construct carrying a demethylase         gene inserted into the genome thereof.

The present disclosure also encompasses a use of any one of the following pluripotent stem cells for differentiation into a desired cell type, in production of a differentiation induction kit for differentiating a pluripotent stem cell into a desired cell type:

-   -   (1) a pluripotent stem cell for differentiation into a desired         cell type, which has a histone in which H3K27me3 modification         has been substantially removed or reduced;     -   (2) a pluripotent stem cell for differentiation into a desired         cell type, in which a demethylase is forcibly expressed; and     -   (3) a pluripotent stem cell for differentiation into a desired         cell type, which has a gene construct carrying a demethylase         gene inserted into the genome thereof.

The present disclosure is specifically described below by way of Examples. However, the present disclosure is not limited thereto. All of these Examples were carried out after being approved by the Ethics Committee of Keio University School of Medicine.

Example 1

(Materials and Methods)

Examples 2 to 7 were carried out using materials and methods described below. The details are as described below.

(Human Pluripotent Stem Cell Culture and Differentiation Induction Methods)

A human ES cell (hESC) lineage SEES-3 was obtained from the National Center for Child Health and Development, Japan (National Research Institute for Child Health and Development). Human induced pluripotent stem cells (hiPSCs) were generated from adult human fibroblasts by introducing mRNAs for POU5F1, SOX2, KLF4, and c-MYC. hESC/iPSCs were maintained under feeder cell-free conditions using StemFitAK-03medium (Ajinomoto) on iMatrix-511 (Nippi)-coated plates. A ROCK inhibitor Y-27632 was added to the medium during cell subculture in order to prevent detachment-induced apoptosis.

For early differentiation, the hESCs were cultured in a differentiation medium of RPMI 1640 (Gibco) supplemented with growth factors (100 ng/ml activin A for endodermal differentiation and 100 ng/ml activin A on Day 1, which was replaced with 10 ng/ml BMP4 and ng/ml bFGF for mesodermal differentiation). For myogenic differentiation, the hPSCs were cultured in a medium of a MEM (Gibco) supplemented with 5% KSR, 1 mM sodium pyruvate, 0.1 mM non-essential amino acids, 2 mM glutamine, 0.1 mM β-mercaptoethanol, and penicillin/streptomycin (50 U/50 μg/ml) on iMatrix-511 or Matrigel (BD)-coated plates.

(Generation of JMJD3c-hESCs)

A full-length human JMJD3 clone was obtained from Addgene (plasmid ID #24167). A point mutation in the catalytic domain was introduced using PrimeSTAR Mutagenesis Basal Kit (Takara). HA-tagged JMJD3c and a mutant thereof were subcloned into a PiggyBac construct containing a tetracycline-responsive element IRES-βgeo, and a puromycin resistance gene controlled by a PGK promoter. Vectors were simultaneously introduced with PiggyBac transposase vectors into hESCs that consistently expressed a reverse tetracycline transactivator (SEE3-1v) using a GeneJuice transfection reagent (Novagen). Stable clones were established by puromycin selection. Inducible expression with doxycycline treatment was confirmed by X-Gal staining.

(Modified mRNA Synthesis and Transfection)

The protein-coding regions (Open Reading Frames, ORFs) of a red fluorescent protein mCherry, a green fluorescent protein Emerald and human influenza virus hemagglutinin (Hemagglutinin, HA)-tagged full-length or catalytic domains of JMJD3, and UTX were subcloned into a pCRII construct containing the 5′ UTR and 3′ UTR of mouse a-globin, which increased mRNA stability and translation efficiency, to prepare templates used to synthesize mRNAs.

Modified mRNAs were synthesized on the basis of the description of the literature “Cell stem cell 7, 618-630 (2010)”. Briefly speaking, a T7 promoter and a poly (A) tail were added through PCR reaction using a KAPA taq kit (Kapa Biosystems). RNAs were synthesized from PCR products using a MEGAscript T7 kit (Ambion) together with ARCA cap analog (New England Biolabs), ATP, GTP, 5-Methyl-CTP (TriLink), and pseudo-UTP (TriLink). The synthetic mRNAs were purified using a MEGAclear kit (Ambion). RNA transfections were performed with Lipofectamine 2000 (Invitrogen) or Lipofectamine Messenger Max (Invitrogen), according to the instructions of the accompanying manual. The B18R interferon inhibitor (eBioscience) was added to the culture medium to increase the viability of the transfected cells. The medium was replaced 2 hours to 3 hours after each transfection.

(Antibody)

The following antibodies were used:

HA (Abcam #ab9110 for immunoblotting method and #ab18181 for immunostaining);

H3K4me3 (Millipore #07-473);

H3K27me3 (Millipore #07-449);

H3K27ac (Active Motif #39-133);

panH3 (Abcam #ab1791); and

MHC (R&D #MAB4470).

(Immunostaining)

The cells were fixed in 4% PFA for 10 minutes at room temperature and permeabilized in 0.5% Triton-X-containing PBS for 10 minutes. The cells were blocked in 2% BSA-containing PBS for 10 minutes, and cultured with primary antibodies in a blocking solution (1:500) for from 2 hours to 3 hours at room temperature or overnight at 4° C. The cells were washed twice in PBS, and then cultured with Alexa dye-conjugated secondary antibodies (Invitrogen) in a blocking solution (1:500) for 1 hour at room temperature. Nuclei were counterstained with DAPI (Dako) for 5 minutes at room temperature. Immunofluorescence was visualized with an inverted fluorescence microscope IX73 (Olympus). Images were obtained using Olympus cellSens imaging software.

(Immunoblotting Method)

The cells were lysed with a sample buffer (50 mM Tris-HCl, pH 6.8, 2% SDS, 6% 2-mercaptoethanol, and 500 mg/ml urea). The proteins were separated by SDS-PAGE using a 4-15% polyacrylamide gel (Biorad) and were electrically transferred to polyvinylidene fluoride membranes (Biorad). The membranes were blocked for 1 hour in 0.1% Tween-20-containing Tris-buffered saline (TBST) and 5% skimmed milk. The membranes were washed in TBST and then incubated with primary antibodies in 2% BSA-containing TBS (1:1,000 dilution) overnight at 4° C. The membranes were washed and then incubated with horseradish peroxidase-conjugated secondary antibodies (GE) for 1 hour at room temperature. The membranes were washed in TEST, and immunoreactivity was visualized using ECL Prime Detection Kit (GE) and detected using Luminescent Image Analyzer (LAS-4000; Fujifilm).

(qRT-PCR)

Total RNA was isolated with TRIzol reagent (Invitrogen), and cDNAs were generated with random hexamers using a Superscript III First-strand Synthesis kit (Invitrogen). Real-time PCR was performed using a SYBR Green PCR system (Takara). The primer sequences used for RT-PCR are listed in Tables 1 and 2 below.

TABLE 1 qRT-PCR Forward GAPDH GGTGGTCTCCTCTGACTTCAACA (SEQ ID NO: 10) POU5F1 CTTGAATCCCGAATGGAAAGGG (SEQ ID NO: 12) NANOG AGAAGGCCTCAGCACCTAC (SEQ ID NO: 14) T GCCCTCTCCCTCCCCTCCACGCACAG (SEQ ID NO: 16) MSX1 CGAGAGGACCCCGTGGATGCAGAG (SEQ ID NO: 18) SOX17 CGCTTTCATGGTGTGGGCTAAGGACG (SEQ ID NO: 20) FOXA2 TGGGAGCGGTGAAGATGGAAGGGCAC (SEQ ID NO: 22) GATA4 GCTCCTTCAGGCAGTGAGAG (SEQ ID NO: 24) GATA6 GTGCCCAGACCACTTGCTAT (SEQ ID NO: 26) GSC CGGTCCTCATCAGAGGAGTC (SEQ ID NO: 28) EVX1 CGGCTGGAGAAGGAATTCTA (SEQ ID NO: 30) MYOG GCCAGACTATCCCCTTCCTC (SEQ ID NO: 32) MEF2C AGGTCACCTGACATCCCAAG (SEQ ID NO: 34) CKM GAAGAGCATGACGGAGAAGG (SEQ ID NO: 36) SIX1 TGTTTGCGCATAAAGGAATG (SEQ ID NO: 38) AFP TGGGACCCGAACTTTCCA (SEQ ID NO: 40) COL2 TTTCCCAGGTCAAGATGGTC (SEQ ID NO: 42) COL1A1 CCTGGATGCCATCAAAGTCT (SEQ ID NO: 44) Reverse GAPDH GTGGTCGTTGAGGGCAATG (SEQ ID NO: 11) POU5F1 GTGTATATCCCAGGGTGATCCTC (SEQ ID NO: 13) NANOG GGCCTGATTGTTCCAGGATT (SEQ ID NO: 15) T CGGCGCCGTTGCTCACAGACCACAGG (SEQ ID NO: 17) MSX1 GGCGGCCATCTTCAGCTTCTCCAG (SEQ ID NO: 19) SOX17 TAGTTGGGGTGGTCCTGCATGTGCTG (SEQ ID NO: 21) FOXA2 TCATGCCAGCGCCCACGTACGACGAC (SEQ ID NO: 23) GATA4 CTGTGCCCGTAGTGAGATGA (SEQ ID NO: 25) GATA6 TGGAGTCATGGGAATGGAAT (SEQ ID NO: 27) GSC CCGAGTCCAAATCGCTTTTA (SEQ ID NO: 29) EVX1 ACACCTTGATGGTGGTTTCC (SEQ ID NO: 31) MYOG GAGGCCGCGTTATGATAAAA (SEQ ID NO: 33) MEF2C GTTAGCCCTCCAACTCCACA (SEQ ID NO: 35) CKM GTTGTCATTGTGCCAGATGC (SEQ ID NO: 37) SIX1 TGGGAAGGAAAATGCAAAAG (SEQ ID NO: 39) AFP GGCCACATCCAGGACTAGTTTC (SEQ ID NO: 41) COL2 CTTCAGCACCTGTCTCACCA (SEQ ID NO: 43) COL1A1 TCTTGTCCTTGGGGTTCTTG (SEQ ID NO: 45)

TABLE 2 ChIP-PCR Forward POU5F1 GGAGGTAAACCCAGCTCACA (SEQ ID NO: 46) NANOG GCTCAGGGATGAGCATGATT (SEQ ID NO: 48) T GGCACGGCCAAATAAGAATA (SEQ ID NO: 50) MSX1 TCCCTCATCTGATCCCAAAC (SEQ ID NO: 52) SOX17 AGCAAGATGCTGGGTGAGTC (SEQ ID NO: 54) FOXA2 TTCTTCGCTCTCAGTGCTCA (SEQ ID NO: 56) GATA4 GATCTTCGCGACAGTTCCTC (SEQ ID NO: 58) GATA6 TGCAGCCTACGCTCTTGTTA (SEQ ID NO: 60) GSC GACATGACGGAGATGGGTCT (SEQ ID NO: 62) EVX1 TCACACTCTCCTCCCCAATC (SEQ ID NO: 64) GAPDH CGGTGACTAACCCTGCGCTCCTG (SEQ ID NO: 66) MYOG_a CCTCCGGAAAGAATGGGACT (SEQ ID NO: 68) MYOG_b TTGGAGCCAAGGTTACCAGT (SEQ ID NO: 70) MYOG_c GGCCTCATTCACCTTCTTGA (SEQ ID NO: 72) MEF2C_a CATGCATTTTCAGGTCACCA (SEQ ID NO: 74) MEF2C_b GCACGTTTAAGACCCCAAAG (SEQ ID NO: 76) SOX1 CCGTCTCACTCCGTCTGAAT (SEQ ID NO: 78) Reverse POU5F1 TTTGGCCTTAGGGTTAAGCA (SEQ ID NO: 47) NANOG TGCCCAGTAACATCCACAAA (SEQ ID NO: 49) T GGTTCAATTCCTGGGTCGTA (SEQ ID NO: 51) MSX1 ACCAGCTCCTACTGCGAGAA (SEQ ID NO: 53) SOX17 CTACACACCCCTGGTTTTGG (SEQ ID NO: 55) FOXA2 GGCGAGTTAAAGGTGTGTACG (SEQ ID NO: 57) GATA4 CATGGCCAAGCTCTGATACA (SEQ ID NO: 59) GATA6 GTCAGTCAAGGCCATCCAC (SEQ ID NO: 61) GSC TGGAAGGTGCCTCACTTCTT (SEQ ID NO: 63) EVX1 TTACAGTACCGCTGGTGACG (SEQ ID NO: 65) GAPDH AGCTAGCCTCGCTCCACCTGACTT (SEQ ID NO: 67) MYOG_a TCTGTTAGCTGCTCTGAGTCT (SEQ ID NO: 69) MYOG_b CTCTCACAGCGCCTCCTG (SEQ ID NO: 71) MYOG_c TGGGCGTGTAAGGTGTGTAA (SEQ ID NO: 73) MEF2C_a CCCCTCCACTTTGATTCGTA (SEQ ID NO: 75) MEF2C_b CGGCCTCAGCTAAATGAAAG (SEQ ID NO: 77) SOX1 AGTGCAGGTCGGTCTCCAT (SEQ ID NO: 79)

{Chromatin Immunoprecipitation (ChIP) Analysis}

The cells were crosslinked with formaldehyde in PBS (final concentration: 1%) at room temperature for 10 minutes. The reaction was quenched with glycine (final concentration: 125 M). The cells were washed with PBS, and stored at −80° C. until use. The cells were lysed in protease inhibitor cocktail-containing Lysis buffer 3 (10 mM Tris-HCl, pH 8.0, 100 mM NaCl, 1 mM EDTA, 0.5 mM EGTA, 0.1% sodium deoxycholate, 0.5% N-lauroylsarcosine). Ultrasonication was performed using Handy Sonic UR-20P (Tomy Seiko Co., Ltd.) so as to generate DNA fragments of from about 150 bp to about 450 bp. The ultrasonicated lysate was diluted with protease inhibitor cocktail-containing ChIP dilution buffer (20 mM Tris-HCl, pH 8.0, 150 mM NaCl, 2 mM EDTA, 1% Triton X-100), and then cultured overnight at 4° C. together with 30 μl of protein G magnetic beads (Invitrogen) precultured with 3 μg of an antibody. The precipitate was washed three times with RIPA buffer (10 mM Tris-HCl, pH 7.5, 140 mM NaCl, 1 mM EDTA, 0.5 mM EGTA, 1% Triton X-100, 0.1% SDS, 0.1% sodium deoxycholate), and then washed once with 10 mM Tris-HCl, pH 8.0, 5 mM EDTA, 10 mM NaCl. Bound chromatin was eluted from the beads in elution buffer (20 mM Tris-HCl, pH 7.5, 5 mM EDTA, 50 mM NaCl, 1% SDS) at 68° C., and decrosslinked at 68° C. for 6 hours. DNA was treated with RNase A and protease K, and then purified by phenol-chloroform-isoamyl alcohol and isopropanol precipitation. Real-time PCR was performed using a SYBR Green PCR system (Takara). The primer sequences are listed in Tables 1 and 2 above.

(Coculture of Myogenic Cells and C2C12 Cells)

Induced myogenic cells were labeled with green fluorescence by introducing Emerald mRNA. The cells were cocultured with C2C12 cells expressing H2B-mCherry in a medium of DMEM (Gibco) supplemented with 2% horse serum.

(Statistical Analysis)

The statistical significance of differences between samples was assessed using Student's t-test for independent samples.

Example 2

(Generation of H3K27me3-deficient Pluripotent Stem Cells (Pluripotent Stem Cells having Histone in which H3K27me3 Modification has been substantially removed or reduced))

In this Example, pluripotent stem cells in which H3K27me3 had been demethylated (H3K27me3-deficient hESCs) were generated. Specifically, in order to demethylate the H3K27me3 of pluripotent stem cells, two methods of manipulating the expression of the demethylase JMJD3 were used. The details are as described below.

(1) Use of Modified Synthetic mRNA

A forced expression system for JMJD3 was generated through use of modified synthetic mRNAs. mRNAs encoding full-length JMJD3 (JMJD3f) and the catalytic domain-containing C-terminus (JMJD3c) were synthesized in vitro (FIG. 5A).

The N-terminus of each of those mRNAs was tagged with a hemagglutinin (HA) sequence for detecting a translated protein. At 8 hours after the introduction of the synthetic mRNAs into hESCs, the demethylation of H3K27me3 was detected by immunostaining and immunoblotting methods (FIG. 5B and FIG. 5C). The results showed that “the introduction of the JMJD3c mRNA induced a more significant decrease in H3K27me3 as compared to the JMJD3f mRNA,” and the results showed that the catalytic domain of JMJD3 was able to sufficiently demethylate a nucleosome histone.

(2) Use of Plasmid Vector having inserted therein Demethylase Gene

A forced expression system for JMJD3c was generated through use of a plasmid vector having introduced therein JMJD3c. More specifically, a hESC line in which the expression of HA-JMJD3c was regulated by doxycycline (Dox) treatment was generated (JMJD3c-hESC) (FIG. 5D). Dox treatment (1 μg/ml) induced HA-JMJD3c expression and a significant decrease in H3K27me3 in all hESCs (FIG. 5F). Forced expression of the JMJD3c mutant, which lacked catalytic function (FIG. 5G), did not induce any change in H3K27me3 (FIG. 5H). Thus, it was confirmed that JMJD3c removed or attenuated H3K27me3 through its demethylase activity.

That is, it was confirmed that pluripotent stem cells in which H3K27me3 modification had been substantially removed or reduced were generated.

It was confirmed that the expression level of H3K27me3 of pluripotent stem cells could be manipulated by each of the above-mentioned two methods. In addition, in the use of the modified synthetic mRNA, the timing and duration time of JMJD3c expression can be regulated, and hence the decrease in the expression level of H3K27me3 (or substantial removal of H3K27me3) can be performed at specific timing at which differentiation of pluripotent stem cells into a desired cell type is induced.

Example 3

(Confirmation of Changes in Developmental Genes in H3K27me3-deficient Pluripotent Stem Cells)

It was revealed that forced expression of JMJD3c (H3K27me3-deficient pluripotent stem cells) resulted in morphological changes in hESCs toward differentiation (FIG. 6A). It was confirmed that the morphological changes occurred even under culture conditions for maintaining an undifferentiated state.

Chromatin immunoprecipitation (ChIP) analysis revealed that decreases in H3K27me3 occurred in the promoters of genes whose gene expression had been upregulated in Dox-treated JMJD3c-hESCs, but those regions were still rich in H3K4me3 (FIG. 6B). This result means that the chromatin structure is brought into an active state.

In this Example, it was shown that, by demethylating H3K27me3, JMJD3c expression was able to cause enhancement of the expression of development/differentiation-related genes over cell differentiation resistance (stem cell-maintaining property).

As described above, forced expression of JMJD3c upregulates the expression of development/differentiation-related genes. In particular, genes associated with endodermal and mesodermal differentiation, such as SOX17, FOXA2, GATA4/6, EOMES, T, and MIXL1, were highly expressed 3 days after the Dox treatment (FIG. 6C). Further, enhancement of the expression of those genes was found also under undifferentiated state-maintaining culture conditions. Typically, the differentiation of hESC/iPSCs into mesoderm/endoderm requires changes into a differentiation medium including various cytokines and growth factors (e.g., activin A, BMP, and FGF). In order to evaluate the influence of JMJD3c on gene expression enhancement for early differentiation, the expression levels of development/differentiation-related genes under JMJD3c-expressed conditions and conventional differentiation conditions were compared to each other. It was confirmed by real-time PCR analysis that JMJD3 upregulated the expression of developmental genes in a non-differentiation medium to a degree similar to that under differentiation conditions using cytokines and growth factors (FIG. 6C).

Those results suggest that ectopic expression (forced expression) of the demethylase allows a transition from a pluripotency-maintaining state to an early differentiation state by directly enhancing the expression of development/differentiation-related genes, and this does not require various cytokines and growth factors. That is, pluripotent stem cells in which H3K27me3 modification has been substantially removed or reduced easily undergo a transition from a pluripotent state to an early differentiation state.

Example 4

(Confirmation of Differentiation of Pluripotent Stem Cells in which Demethylase is forcibly expressed into Desired Cell Type)

In the above-mentioned Examples, it was confirmed that H3K27 demethylation by JMJD3c changes the chromatin structure of hESCs to an active form for highly efficient induction of differentiation into a desired cell type. In view of this, it was considered that, when a transcription factor required for induction of differentiation into a desired cell type was introduced, differentiation into the desired cell type was able to be induced with high efficiency. Accordingly, in this Example, as an example of induction of differentiation into a desired cell type, a myogenic differentiation model using a myogenesis-regulating master transcription factor MYOD1 was adopted. It is known that forced expression of MYOD1 alone cannot cause sufficient epigenetic changes and transcriptional changes in hESCs, resulting in poor myogenic conversion (see Cell Reports 3, 661-670 (2013)).

In order to confirm whether JMJD3c was able to facilitate MYOD1-induced muscle cell differentiation, JMJD3c was transiently forcibly expressed in hESCs before forced expression of MYOD1 (FIG. 7A).

In this process, the JMJD3c-hESC line was used, and induced by introducing JMJD3c and MYOD1 by means of Dox treatment and synthetic mRNA, respectively.

Alterations in the expression of four genes (MYOG, MEF2C, CKM, and SIX1) serving as markers for skeletal muscle differentiation were examined. Real-time PCR analysis revealed that forced expression of MYOD1 alone did not induce upregulation of the expression of the muscle cell differentiation-related genes except SIX1.

However, when JMJD3c was forcibly expressed before forced expression of MYOD1, all of those genes showed significant expression upregulation. However, forced expression of JMJD3c alone did not alter the expression pattern of MYOD1 downstream genes. Those results confirmed that JMJD3c facilitated muscle differentiation mediated by MYOD1 gene expression.

Further, chromatin changes in the promoter regions of MYOG and MEF2C during differentiation mediated by forced expression of MYOD1 with or without forced expression of JMJD3c were examined using ChIP assay. It was revealed that the levels of H3K4me3 and H3K27me3 in those regions were lower than those of a positive control, such as GAPDH, POU5F1, or Brachyury (T), in both the hESCs and the differentiated cells (FIG. 7C), and there was no large difference between a JMJD3c-positive condition and a negative condition. Meanwhile, it was revealed that those regions were significantly enriched for H3K27 acetylation (H3K27ac) in the differentiated cells only under the JMJD3c-positive condition, but not under the negative condition (FIG. 7C). H3K27ac has been known to be directly involved in active transcription. Thus, it was suggested that the combination of JMJD3c and MYOD1 formed an active state of chromatin in myogenic genes.

Further, it was confirmed that JMJD3c/MYOD1-forcibly expressing hESCs were myosin heavy chain (MHC)-positive, and changed to myotube-like morphology at 4 days post differentiation (FIG. 7D). The percentage of MHC-positive cells was much higher than the percentage observed under the condition of overexpressing MYOD1 alone (FIG. 7E). Those results show that JMJD3c facilitates MYOD1-mediated differentiation of hESCs into skeletal muscle cells. However, forced expression of the JMJD3c mutant did not induce MYOD1-mediated myogenic differentiation (FIG. 7F and FIG. 7G). Thus, it was confirmed that the demethylation of H3K27me3 was essential to MYOD1-mediated differentiation of hESCs into muscle cells.

As apparent from the foregoing, differentiation into a desired cell type can be efficiently induced by introducing a transcription factor required for induction of differentiation into the desired cell type into H3K27me3-deficient cells (pluripotent stem cells having a histone in which H3K27me3 modification has been substantially removed or reduced).

Example 5

(Confirmation of Differentiation of Pluripotent Stem Cells into Desired Cell Type using Synthetic mRNA)

In Example 4 described above, it was confirmed that forced expression of the demethylase was able to facilitate MYOD1-mediated differentiation of hESCs into skeletal muscle cells.

In this Example, it was confirmed whether differentiation of hESCs into skeletal muscle cells was able to be induced by using only synthetic mRNAs for the demethylase JMJD3c and the transcription factor MYOD1 required for induction of differentiation into a desired cell type without altering the DNA of the pluripotent stem cells.

The mRNA for JMJD3c was transfected into hESCs twice, followed by three transfections with the MYOD1 mRNA (FIG. 8A). Two days after the last transfection of the MYOD1 mRNA, the majority of hESCs were differentiated into MHC-positive cells (FIG. 8B and FIG. 8C). As a control, hESCs were transfected with mRNAs for mCherry and MYOD1, but myogenic differentiation was not induced.

Some MHC-positive cells appeared to be fused cells (FIG. 8D), which was able to be further confirmed by a fusion assay with mouse C2C12 cells (FIG. 8E). Those results were able to confirm that the induced myotube-like cells became mature skeletal muscles in vitro.

Further, it was confirmed that the mRNA for JMJD3c facilitated MYOD1-mediated myogenic differentiation of fibroblast-derived hiPSCs (FIG. 8F and FIG. 8G). This suggests that JMJD3c facilitates direct conversion from a pluripotent state to a terminal differentiation state.

As apparent from the foregoing, differentiation into a desired cell type can be induced with high efficiency by introducing (adding) a transcription factor required for induction of differentiation into the desired cell type into pluripotent stem cells in which H3K27me3 modification has been substantially removed or reduced.

In related art, it is shown that skeletal muscle cells can be induced even when MYOD1 is used alone. However, in Non Patent Literature 4, drug selection needs to be performed in order to stably express the MYOD1 gene, and preculture is required for about 10 days prior to the initiation of differentiation induction. In addition, in Non Patent Literature 3, a PAX7 gene is introduced instead of the MYOD1 gene, but differentiation induction requires culture for about 1 month.

In addition, there is a report that skeletal muscle differentiation is induced by introducing a gene called BAF60C, and then introducing the MYOD1 gene (see Cell Rep. 2013 Mar. 28; 3 (3): 661-70.). However, differentiation induction takes 20 days, and requires the use of a lentiviral vector.

Example 6

(Transcription factors differentiate Pluripotent Stem Cells into Desired Cell Types)

In Examples 4 and 5 described above, it was confirmed that MYOD1-mediated induction of differentiation of hESCs into skeletal muscle cells was able to be facilitated by forcibly expressing the demethylase or adding the synthetic mRNA for the demethylase.

In this Example, it was confirmed whether differentiation of pluripotent stem cells into a plurality of desired cell types was able to be induced using respective transcription factors.

With reference to the method described in Example 4, JMJD3c-hESCs were treated with Dox (+JMJD3c) or without Dox (−JMJD3c) on from Day 1 to Day 2 after plating, and then, during Day 2, synthetic mRNA for TCF1, SOX9, RUNX3, or mCherry was introduced twice. The cells were collected on Day 4, and the expression of each differentiation marker gene was examined by RT-qPCR analysis.

The analysis results are shown in FIG. 9. In the cells transfected with the TCF1 transcription factor, AFP serving as a marker gene for hepatoblasts was significantly increased. In the cells transfected with the SOX9 transcription factor, COL2 serving as a marker gene for chondrocytes was significantly increased. In the cells transfected with the RUNX3 transcription factor, COL1A1 serving as a marker gene for osteoblasts was significantly increased.

Thus, it was confirmed that differentiation into desired cell types were able to be efficiently induced by introducing the transcription factors required for induction of differentiation into the desired cell types into H3K27me3-deficient cells (pluripotent stem cells having a histone in which H3K27me3 modification has been substantially removed or reduced).

Example 7

(Examples of Differentiation into Desired Cell Types using Pluripotent Stem Cells of the Present Disclosure)

In this Example, differentiation into various desired cell types was confirmed using pluripotent stem cells having a histone in which H3K27me3 modification had been substantially removed or reduced.

(Differentiation into Skeletal Muscle Cells)

With reference to the description of Example 5, during 4-day culture, human pluripotent stem cells were transfected with the JMJD3c gene (SEQ ID NO: 80) twice, and then transfected with the MYOD1 gene (SEQ ID NO: 86, SEQ ID NO: 88) three times. It was confirmed that the cells were differentiated into skeletal muscle cells through the 4-day culture.

(Differentiation into Liver Cells)

With reference to the description of Example 5, during 4-day culture, human pluripotent stem cells were transfected with the JMJD3c gene (SEQ ID NO: 80) twice, and then transfected with the HNF1A gene (SEQ ID NO: 87, SEQ ID NO: 94) three times. It was confirmed that the cells were differentiated into liver cells through the 4-day culture.

(Differentiation into Nerve Cells)

With reference to the description of Example 5, during 4-day culture, human pluripotent stem cells were transfected with the JMJD3c gene (SEQ ID NO: 80) twice, and then transfected with the NEUROG1 gene (SEQ ID NO: 81, SEQ ID NO: 89), the NEUROG2 gene (SEQ ID NO: 82, SEQ ID NO: 90), the NEUROG3 gene (SEQ ID NO: 83, SEQ ID NO: 91), the NEUROD1 gene (SEQ ID NO: 84, SEQ ID NO: 92), and the NEUROD2 gene (SEQ ID NO: 85, SEQ ID NO: 93) three times. It was confirmed that the cells were differentiated into nerve cells through the 4-day culture.

(Subject Matter of the Present Invention)

It has been confirmed that, in the method of the present disclosure, a differentiation efficiency of from 60% to 70% is achieved in 4 days from the initiation of differentiation induction without the addition of various cytokines and growth factors required for causing a transition from a pluripotent state to an early differentiation state and with only the addition of synthetic mRNA to pluripotent stem cells. That is, in the method of the present disclosure, differentiation induction can be achieved within a shorter period and with higher efficiency without requiring the various cytokines and growth factors that are required in related-art methods.

In Examples of the present disclosure, even when there was no environmental change, a histone demethylase {in particular, the catalytic domain of JMJD3 (JMJD3c)} enhanced the expression of development/differentiation-related genes in pluripotent stem cells, and facilitated the conversion of a gene expression pattern from a pluripotent stem cell pattern to a gene expression pattern of a differentiated cell. This suggests that, without being limited to JMJD3, any demethylase having an effect of removing or attenuating methylation suppressing the expression of development/differentiation-related genes can facilitate cell differentiation of pluripotent stem cells into differentiated cells.

In Examples of the present disclosure, it has been shown that the histone demethylase JMJD3 cancels the suppression of the expression of the differentiation-related genes by rapidly attenuating the methylation of H3K27. Particularly when modified synthetic mRNA for JMJD3c was used, significant attenuation of H3K27me3 was confirmed in several hours. Those results show that the histone demethylase antagonistically regulates H3K27 methylation by a PcG complex in human pluripotent stem cells.

In the pluripotent stem cells, forced expression of the histone demethylase caused demethylation of H3K27me3, and upregulated gene expression of many development/differentiation-related genes. Those changes were also found under human pluripotent stem cell culture conditions for maintaining pluripotency. The mutant of the histone demethylase (function-deficient mutant of JMJD3c) did not induce those phenomena, revealing that specific demethylation of H3K27 by the demethylase was directly involved in the increase of the transcription activity of development/differentiation-related genes.

In Examples of the present disclosure, it has also been revealed that, in the group of development/differentiation-related genes whose gene expression is upregulated by the demethylase activity of JMJD3, more mesodermal/endodermal differentiation related genes are included than genes involved in ectodermal differentiation. This shows that the demethylase activity of the JMJD3 gene effectively facilitates differentiation into mesendodermal cells, specifically bone, muscle, liver, circulatory, digestive, and reproductive cells. However, the demethylase activity of JMJD3 gene also upregulated the expression of a group of genes involved in ectodermal differentiation as compared to that in pluripotent stem cells, and hence is likely involved also in facilitating differentiation into, for example, nerve and epidermal cells.

H3K27me3 is not present in large amounts in the promoter regions of muscle cell differentiation-related genes in hESCs, and hence the demethylase activity of JMJD3c is considered to be indirectly involved in enhancement of the expression of the muscle cell differentiation-related genes via enhancement of the expression of a gene involved in early development/cell differentiation.

Thus, it has been shown that the demethylase activity allows the state of cells to undergo a transition from a pluripotency-maintaining state to a differentiated state by attenuating differentiation resistance of pluripotent stem cells. The attenuation of the differentiation resistance is not limited to only the activation of muscle differentiation-related genes, but also facilitates the activation of other differentiated cell genes.

INDUSTRIAL APPLICABILITY

According to the present disclosure, the novel method of differentiating a pluripotent stem cell into a desired cell type with high efficiency can be provided. 

1.-16. (canceled)
 17. A differentiation induction kit for differentiating a pluripotent stem cell into a desired cell type, comprising at least any one of the following items (1) to (3): (1) a pluripotent stem cell having a histone in which H3K27me3 modification has been substantially removed or reduced; (2) a pluripotent stem cell in which JMJD3 is forcibly expressed; and (3) a pluripotent stem cell having a gene construct carrying JMJD3 inserted into a genome thereof, wherein the JMJD3 has demethylase activity that induces differentiation of the pluripotent stem cell by removing a methyl group of H3K27me3.
 18. The differentiation induction kit according to claim 17, wherein the JMJD3 is a demethylase containing only an enzymatically active region of JMJD3.
 19. The differentiation induction kit according to claim 17, wherein the JMJD3 has an amino acid sequence set forth in any one of SEQ ID NOS: 1 to
 3. 20. The differentiation induction kit according to claim 17, further comprising a transcription factor required for induction of differentiation into the desired cell type.
 21. The differentiation induction kit according to claim 17, wherein the desired cell type is a skeletal muscle cell, comprising at least any one of the following items (1) to (3): (1) a pluripotent stem cell having a histone in which H3K27me3 modification has been substantially removed or reduced, and a transcription factor MYOD1; (2) a pluripotent stem cell in which JMJD3 is forcibly expressed, and a transcription factor MYOD1; and (3) a pluripotent stem cell having a gene construct carrying JMJD3 inserted into a genome thereof, and a transcription factor MYOD1.
 22. The differentiation induction kit according to claim 17, wherein the desired cell type is a nerve cell, comprising at least any one of the following items (1) to (3): (1) a pluripotent stem cell having a histone in which H3K27me3 modification has been substantially removed or reduced, and a transcription factor NEUROG1, NEUROG2, NEUROG3, NEUROD1, and/or NEUROD2; (2) a pluripotent stem cell in which JMJD3 is forcibly expressed, and a transcription factor NEUROG1, NEUROG2, NEUROG3, NEUROD1, and/or NEUROD2; and (3) a pluripotent stem cell having a gene construct carrying JMJD3 inserted into a genome thereof, and a transcription factor NEUROG1, NEUROG2, NEUROG3, NEUROD1, and/or NEUROD2.
 23. The differentiation induction kit according to claim 17, wherein the desired cell type is a liver cell, comprising at least any one of the following items (1) to (3): (1) a pluripotent stem cell having a histone in which H3K27me3 modification has been substantially removed or reduced, and a transcription factor HNF1A; (2) a pluripotent stem cell in which JMJD3 is forcibly expressed, and a transcription factor HNF1A; and (3) a pluripotent stem cell having a gene construct carrying JMJD3 inserted into a genome thereof, and a transcription factor HNF1A. 